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technical article
Variable area flow measurement instrument in automatic process control of metal tube float flowmeter
2012-3-28 14:27:44

测量流量时一定要准确知道被量程介质的密度,管径及压力、流量的大小,参数越精确,金属管浮子流量计做出来的精度就越高。 When selecting a metal tube float flowmeter , you must know exactly the density of the medium being measured, the diameter of the pipe, the pressure, and the size of the flow. The more accurate the parameters, the higher the accuracy of the metal tube float flowmeter. Metal tube float flowmeter is a variable area flow measurement instrument commonly used in industrial automation process control. It has the characteristics of small size, large detection range and convenient use. It can be used to measure the flow of liquid, gas and steam, especially suitable for medium flow measurement with low flow rate and small flow.


Measurement features:


1. Robust all-metal structure design type float flow meter 2. Measuring tube indicator with independent concept design 3. Stainless steel, Hastelloy, titanium, PTFE material measurement system can be selected 4. Low pressure loss design 5. Short stroke 、 Small structure design, total instrument height 250 6.Magnetic coupling structure to ensure data transmission, more stable signal 7, insulation or heat tracing jacket 8, vertical, horizontal, various installation methods are more suitable for different use occasions 9, suitable for small diameter And low-velocity medium flow measurement 10. Reliable work, low maintenance and long life 11. Low requirements for straight pipe sections 12, wide flow ratio 10: 1 13, dual-line large LCD display, optional on-site instantaneous / cumulative flow Display with backlight

The flow detection element of the metal tube float flowmeter is composed of a vertically conical tube that expands from bottom to top and a float group that moves up and down along the axis of the cone tube. 检测部分是由一个自下向上扩张的垂直锥形管和一个沿着锥形管轴可以上下自由移动的浮子组成。 The detection part of the metal tube float flowmeter is composed of a vertically conical tube that expands from the bottom up and a float that can move freely up and down along the axis of the conical tube. When the measured fluid passes from the bottom to the ring gap formed by the cone tube and the float, a differential pressure is generated at the upper and lower ends of the float to form a rising force of the float. When the rising force of the float is greater than the weight of the float immersed in the fluid, the float rises. The gap area increases accordingly, the fluid flow velocity at the annulus decreases immediately, the differential pressure at the upper and lower ends of the float decreases, and the lifting force acting on the float also decreases. A height. The height of the float in the cone has a corresponding relationship with the flow rate.

的流量检测元件是由一根自下向上扩大的垂直锥形管和一个沿着锥管轴上下移动的浮子组所组成。 The flow detection element of the metal float flowmeter is composed of a vertically tapered tube that expands from bottom to top and a float group that moves up and down along the axis of the cone tube. When the measured fluid passes from the bottom to the ring gap 3 formed by the cone 1 and the float 2, a differential pressure is generated at the upper and lower ends of the float to form a rising force of the float. When the rising force of the float is greater than the weight of the float immersed in the fluid, the float rises. The ring gap area increases, the fluid velocity at the ring gap immediately decreases, the differential pressure at the upper and lower ends of the float decreases, and the lifting force acting on the float also decreases. Until the rising force equals the weight of the float immersed in the fluid, the float is stable. At a certain height. The height of the float in the cone has a corresponding relationship with the flow rate. The basic equation of the volume flow Q is (1) when the float is a non-solid core hollow structure (load adjustment amount), then in the formula (2) α-the flow coefficient of the meter, which varies with the shape of the float; ε-is The gas expansion coefficient when the measured fluid is gas is usually ignored due to the small correction amount of this coefficient, and it has been included in the flow coefficient through verification. If it is a liquid, ε = 1; △ F——circulation annular area, m2; g——local gravity acceleration, m / s2; Vf——volume of float, if it is extended, it should also include, m3; ρf——density of float material, kg / m3; ρ——density of measured fluid, if Gas is the density on the upstream cross section of the float, kg / m3; Ff-cross-sectional area at the working diameter (maximum diameter) of the float, m2; Gf-mass of the float, kg. The relationship between the circulation ring area and the height of the float is shown in equation (3). When the structural design has been determined, d and β are constant. There is a quadratic term of h in the formula. Generally, this nonlinear relationship cannot be ignored. Only when the cone angle is very small can it be regarded as approximately linear. m2 (3) where d——the maximum diameter of the float (that is, working diameter), m; h——the height of the float from the cone diameter equal to the maximum diameter of the float, m; β——the cone angle of the cone; a, b --constant. Typical structure of 15-40mm transparent cone tube float flowmeter. The most commonly used transparent conical tube 4 is made of borosilicate glass, and it is customarily referred to as a glass tube float flow meter. The flow indexing is directly engraved on the outer wall of the cone tube 4, and an indexing scale is also installed beside the cone tube. The inner cavity of the cone tube has two types: a smooth surface of the cone and a rib (or plane) with a guide. The float moves freely in the cone tube, or moves under the guidance of the ribs of the cone tube, and the instrument with a smooth inner surface of a larger mouth is also guided by a guide rod. Typical structure of metal tube float flow meter with right-angle installation, usually suitable for instruments with a diameter of 15-40mm or more. The cone tube 5 and the float 4 constitute a flow detection element. There is an extension of the guide rod 3 in the sleeve, and the displacement of the float is transmitted to the conversion part outside the sleeve through a magnetic steel coupling method. The conversion part has two types: local indication and remote signal output. In addition to the right-angle installation structure, there is a straight-through structure with the inlet and outlet center lines concentric with the tapered tube, which is usually used for instruments with a diameter of less than 10-15mm.